A white light-emitting device including a blue light-emitting element including a nitride semiconductor element as a light-emitting element and a phosphor has recently increasingly been used for a backlight of a large-sized liquid crystal television or a light source for lighting equipment. In such a product as a large-sized liquid crystal television or lighting equipment, many white light-emitting devices are used in one product. Therefore, blue light-emitting elements included in such products are required to be high in quality in mass production.
A nitride semiconductor light-emitting element included in a backlight of a large-sized liquid crystal television or a light source for lighting equipment has increasingly generally been driven in a relatively high-current region, for example, at 80 mA or higher. A conventional nitride semiconductor light-emitting element is driven in a relatively low-current region around 20 mA in many cases.
In some conventional nitride semiconductor light-emitting elements, a nitride semiconductor layer is formed on a C plane of a sapphire substrate and light from a light-emitting layer is extracted not only from the nitride semiconductor layer but also from a side surface of the sapphire substrate. In such a nitride semiconductor light-emitting element, the sapphire substrate should have a thickness large to some extent. In order to prevent light emitted from the side surface of the sapphire substrate from returning to the inside of the sapphire substrate as a result of total reflection by the side surface of the sapphire substrate, the side surface of the sapphire substrate should also be roughened.
For example, Japanese Patent Laying-Open No. 2010-141331 (PTD 1) describes growing a light-emitting structure on a substrate, thereafter forming a division groove like a dotted line in the substrate with laser beams, and thereafter dividing the substrate and the light-emitting structure by applying a pressure to the substrate. Japanese Patent Laying-Open No. 2013-21250 (PTD 2) describes formation of an affected layer in a side surface of a sapphire substrate by emitting laser beams from an upper surface side or a lower surface side of the sapphire substrate.
PTD 1: Japanese Patent Laying-Open No. 2010-141331
PTD 2: Japanese Patent Laying-Open No. 2013-21250